GF47.30-P-3015MIK Purge Function
GF47.30-P-3015MIK Purge Function
- MODEL 171.454 with ENGINE 272.942 as of Model Year 09 /AEJ 08 model refinement package
- MODEL 171.458 with ENGINE 272.969 as of Model Year 09 /AEJ 08 model refinement package
Schematic diagram of fuel tank aeration and ventilation (except Code (494) USA version)
45 Fuel filler neck
45/2 Float with flap
58 Fluid reservoir
75 Fuel tank
75/3 Vent and breather pipe
76 Vent valve
77 Activated charcoal canister
Y58/1 Purge control valve
A Air admission line and vent line
B Purge line
Purging function requirements, general
- Circuit 87M ON (engine control ON)
- Engine started for at least 45 s
- Coolant temperature greater than 40°C
- Engine not in deceleration mode
- Engine not in the lambda adaptation phase
Purging, general
When the fuel tank is being ventilated, no fuel vapors should escape into the outside air.
The fuel vapors are stored in the activated charcoal canister and burnt later in the engine.
In order to enable the purging, the ME-SFI control unit (N3/10) reads the following sensors:
- Hot film MAF sensor (B2/5), engine load
- Intake air temperature sensor (B2/5b1)
- Coolant temperature sensor (B11/4)
- Crankshaft Hall sensor (B70), motor speed
- LH and RH O2 sensors upstream of CAT, oxygen sensor signals
- LH and RH O2 sensors downstream of CAT, oxygen sensor signals
Purging function sequence
The fuel tank is ventilated through the aeration/ventilation pipe, the vent valve and the activated charcoal canister.
For fuel tank ventilation, the vent valve opens at an overpressure of about 30 to 50 mbar. This causes the fuel vapors to flow to the activated charcoal canister, where they are stored and drawn off into the intake manifold when purging is enabled.
When the engine is running, the fuel vapors stored in the activated charcoal canister, are drawn off through the purge control valve (Y58/1) and combusted in the engine.
To control the purging quantity, the ME-SFI control unit actuates the purging switchover valve at the ground end with a PWM signal (at a frequency of 10 Hz).
The purge quantity is determined by continuously opening and closing the purge control valve with on-periods of varying durations.
The idle speed control prevents the purging from causing a change in rpm when the engine is at idle. A leaner fuel-air mixture is produced in line with the charge of the activated charcoal canister with the fuel vapors.
